Electronic devices (also referred to herein as modules) typically include a relatively small number of terminals and each terminal is typically dedicated to a specific purpose. For example, certain electronic modules have only a terminal dedicated for providing power to the module, a terminal dedicated for providing ground, and a terminal dedicated for providing output data. No terminal is provided for inputting data to such modules. A small number of dedicated terminals minimizes overall module size and simplifies the interface. Therefore, adding a new terminal for an additional purpose is undesirable, particularly if the additional purpose is not needed during mission mode operations. Including a terminal that is useful only during a configuration mode operation is undesirable for a variety of reasons. For example, an additional terminal consumes valuable space and materials and increases interface complexity, which in turn increases the risk of confusion as to which terminal is which.
Programming an electronic sensor module with sensor calibration data is one example of a function for which an additional terminal might be needed during only a limited portion of a module's lifetime. Electronic sensor modules and other similar electronic devices typically require some form of calibration of their output to compensate for incidental design variations that occur during manufacturing or other changes that occur during operational use. Electrical calibration is performed, for example, by first manufacturing the sensor module, stimulating the completed sensor module with a known stimulus, comparing the module's output with an expected output corresponding to the known stimulus, and recording in a memory a table of calibration data that is thereafter referenced by the sensor module when outputting sensor readings. Consequently, the sensor module is able to compensate for any variations detected with respect to the expected output corresponding to the known stimulus. After the electronic sensor module is calibrated and performing its sensing function, additional data input is rarely, if ever, required. Therefore, use of a dedicated terminal for entering calibration data is undesirable because the dedicated terminal would have little use relative to other terminals while consuming valuable space and materials and increasing interface complexity.
A variety of techniques exist for loading calibration data into an electronic sensor module or other electronic module without using a dedicated terminal. However, certain existing techniques require integration of overdriving circuitry into the electronic module, which consumes a large area and large amounts of power. Moreover, many existing techniques preclude or prevent any data from being output by the electronic module while calibration data is loaded.